There is a typical image forming apparatuses such as a multi-functional peripheral (MFP) that prints documents and images.
To save energy in the typical image forming apparatus, if a preset time elapses while the user is not using the image forming apparatus, the power supply to units that largely consume electric power is stopped and the image forming apparatus enters a standby state in which electric power is supplied only to some functions to reduce power consumption (the standby state will be referred to below as the standby mode).
Once the image forming apparatus enters the standby mode, however, it takes time for the image forming apparatus to return to a state in which the user may use the image forming apparatus (the state will be referred to below as the normal mode).
If, for example, a host computer transmits information requesting data to an image forming apparatus placed in the standby mode via a network to check information about the image forming apparatus, the image forming apparatus shifts from the standby mode to the normal mode before transmitting response data. If the host computer transmits information requesting data many times, the number of shifts from the standby mode to the normal mode is increased and the time during which the image forming apparatus is placed in the standby mode is shortened. This prevents power consumption from being efficiently reduced.
To deal with the above-description, it is known to provide an image forming apparatus that has a controller including, for example, two central processing units (CPUs), one of which is a main CPU that responds in the normal mode and the other of which is a sub-CPU that responds in the standby mode, the main CPU stores response data in a random-access memory (RAM) in the main CPU.
When the known image forming apparatus shifts to the standby mode, the sub-CPU retrieves preset response data from the RAM in the main CPU and stores the response data in a RAM in the sub-CPU. When the image forming apparatus shifts from the normal mode to the standby mode, part of response data is stored in the RAM in the sub-CPU. In the standby mode, the sub-CPU may generate response data from data stored in the RAM of the sub-CPU and may transmit the response data.
Each time the known image forming apparatus shifts to the standby mode, however, data in the RAM in the main CPU needs to be transferred to the RAM in the sub-CPU. This takes time to shift until the image forming apparatus enters the standby mode.